Integrated Circuit Contactor For Testing ICs And Method Of Construction

ABSTRACT

The terminals of a device under test (DUT) are temporarily electrically connected to corresponding contact pads on a load board by a series of electrically conductive pin pairs. The pin pairs are protected against damage from balls on a DUT by a protective ball guide which includes recesses for receiving part of the ball but prevents the ball from driving the pins beyond a limited range. The ball guide provides fine alignment horizontally and vertically enabling stable electrical performance.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure is directed to equipment for testingmicrocircuits.

Description of the Related Art

As microcircuits continually evolve to be smaller and more complex, thetest equipment that tests the microcircuits also evolves. There is anongoing effort to improve microcircuit test equipment, with improvementsleading to an increase in reliability, an increase in throughput, and/ora decrease in expense.

Mounting a defective microcircuit on a circuit board is relativelycostly. Installation usually involves soldering the microcircuit ontothe circuit board. Once the microcircuit is mounted on a circuit board,removing a microcircuit is problematic because the very act of meltingthe solder for a second time ruins the circuit board. Thus, if themicrocircuit is defective, the circuit board itself is probably ruinedas well, meaning that the entire value added to the circuit board atthat point is lost. For all these reasons, a microcircuit is usuallytested before installation on a circuit board.

Each microcircuit must be tested in a way that identifies all defectivedevices, but yet does not improperly identify good devices as defective.Either kind of error, if frequent, adds substantial overall cost to thecircuit board manufacturing process, and can add retest costs fordevices improperly identified as defective devices.

Microcircuit test equipment itself is quite complex. First of all, thetest equipment must make accurate and low resistance temporary andnon-destructive electrical contact with each of the closely spacedmicrocircuit contacts. Because of the small size of microcircuitcontacts and the spacings between them, even small errors in making thecontact will result in incorrect connections. Connections to themicrocircuit that are misaligned or otherwise incorrect will cause thetest equipment to identify the device under test (DUT) as defective,even though the reason for the failure is the defective electricalconnection between the test equipment and the DUT rather than defects inthe DUT itself.

A further problem in microcircuit test equipment arises in automatedtesting. Testing equipment may test 100 devices a minute, or even more.The sheer number of tests cause wear on the tester contacts makingelectrical connections to the microcircuit terminals during testing.This wear dislodges conductive debris from both the tester contacts andthe DUT terminals that contaminates the testing equipment and the DUTsthemselves.

The debris eventually results in poor electrical connections duringtesting and false indications that the DUT is defective. The debrisadhering to the microcircuits may result in faulty assembly unless thedebris is removed from the microcircuits. Removing debris adds cost andintroduces another source of defects in the microcircuits themselves.

Other considerations exist as well. Inexpensive tester contacts thatperform well are advantageous. Minimizing the time required to replacethem is also desirable, since test equipment is expensive. If the testequipment is off line for extended periods of normal maintenance, thecost of testing an individual microcircuit increases.

Test equipment in current use has an array of test contacts that mimicthe pattern of the microcircuit terminal array. The array of testcontacts is supported in a structure that precisely maintains thealignment of the contacts relative to each other. An alignment templateor board aligns the microcircuit itself with the test contacts. The testcontacts and the alignment board are mounted on a load board havingconductive pads that make electrical connection to the test contacts.The load board pads are connected to circuit paths that carry thesignals and power between the test equipment electronics and the testcontacts.

For the electrical tests, it is desired to form a temporary electricalconnection between each terminal on the device under test and acorresponding electrical pad on a load board. In general, it isimpractical to solder and remove each electrical terminal on themicrocircuit being contacted by a corresponding electrical probe on thetestbed. Instead of soldering and removing each terminal, the tester mayemploy a series of electrically conductive pins arranged in a patternthat corresponds to both the terminals on the device under test and theelectrical pads on the load board. When the device under test is forcedinto contact with the tester, the pins complete the circuits betweenrespective device under test contacts and corresponding load board pads.After testing, when the device under test is released, the terminalsseparate from the pins and the circuits are broken.

The present application is directed to improvements to these pins.

There is a type of testing known as “Kelvin” testing, which measures theresistance between two terminals on the device under test. Basically,Kelvin testing involves forcing a current to flow between the twoterminals, measuring the voltage difference between the two terminals,and using Ohm's Law to derive the resistance between the terminals,given as the voltage divided by the current. Each terminal on the deviceunder test is electrically connected to two contact pads on the loadboard. One of the two pads supplies a known current amount of current.The other pad is a high-impedance connection that acts as a voltmeter,which does not draw any significant amount of current. In other words,each terminal on the device under test that is to undergo Kelvin testingis simultaneously electrically connected to two pads on the loadboard—one pad supplying a known amount of current and the other padmeasuring a voltage and drawing an insignificant amount of current whiledoing so. The terminals are Kelvin tested two at a time, so that asingle resistance measurement uses two terminals on the load board andfour contact pads.

In this application, the pins that form the temporary electricalconnections between the device under test and the load board may be usedin several manners. In a standard (non-kelvin) test, each pin connects aparticular terminal on the device under test to a particular pad on theload board, with the terminals and pads being in a one-to-onerelationship. For these standard tests, each terminal corresponds to onepad, and each pad corresponds to one terminal.

There are many aspects of the testbeds that may be incorporated fromolder or existing testbeds. For instance, much of the mechanicalinfrastructure and electrical circuitry may be used from existing testsystems, and may be compatible with the electrically conductive pinsdisclosed herein. Such existing systems are listed and summarized below.

An exemplary microcircuit tester is disclosed in United States PatentApplication Publication Number US 2007/0202714, titled “Test ContactSystem For Testing Integrated Circuits With Packages Having An Array OfSignal And Power Contacts”, invented by Jeffrey C. Sherry, published onAug. 30, 2007 and incorporated by reference herein in its entirety.

For the tester of '714, a series of microcircuits is testedsequentially, with each microcircuit, or “device under test”, beingattached to a testbed, tested electrically, and then removed from thetestbed. The mechanical and electrical aspects of such a testbed aregenerally automated, so that the throughput of the testbed may be keptas high as possible.

In '714, a test contact element for making temporary electrical contactwith a microcircuit terminal comprises at least one resilient fingerprojecting from an insulating contact membrane as a cantilevered beam.The finger has on a contact side thereof, a conducting contact pad forcontacting the microcircuit terminal. Preferably the test contactelement has a plurality of fingers, which may advantageously have apie-shaped arrangement. In such an arrangement, each finger is definedat least in part by two radially oriented slots in the membrane thatmechanically separate each finger from every other finger of theplurality of fingers forming the test contact element.

In '714, a plurality of the test contact elements can form a testcontact element array comprising the test contact elements arranged in apredetermined pattern. A plurality of connection vias are arranged insubstantially the predetermined pattern of the test contacts elements,with each of said connection vias is aligned with one of the testcontact elements. Preferably, an interface membrane supports theplurality of connection vias in the predetermined pattern. Numerous viascan be embedded into the pie pieces away from the device contact area toincrease life. Slots separating fingers could be plated to create anI-beam, thereby preventing fingers from deforming, and also increasinglife.

The connection vias of '714 may have a cup shape with an open end, withthe open end of the cup-shaped via contacting the aligned test contactelement. Debris resulting from loading and unloading DUTs from the testequipment can fall through the test contact elements where thecup-shaped vias impound the debris.

The contact and interface membranes of '714 may be used as part of atest receptacle including a load board. The load board has a pluralityof connection pads in substantially the predetermined pattern of thetest contacts elements. The load board supports the interface membranewith each of the connection pads on the load board substantially alignedwith one of the connection vias and in electrical contact therewith.

In '714, the device uses a very thin conductive plate with retentionproperties that adheres to a very thin non-conductive insulator. Themetal portion of the device provides multiple contact points or pathsbetween the contacting I/O and the load board. This can be done eitherwith a plated via hole housing or with plated through hole vias, orbumped surfaces, possibly in combination with springs, that has thefirst surface making contact with the second surface, i.e., the deviceI/O. The device I/O may be physically close to the load board, thusimproving electrical performance.

One particular type of microcircuit often tested before installation hasa package or housing having what is commonly referred to as a ball gridarray (BGA) terminal arrangement. A typical BGA package may have theform of a flat rectangular block, with typical sizes ranging from 5 mmto 40 mm on a side and 1 mm thick.

A typical microcircuit has a housing enclosing the actual circuitry.Signal and power (S&P) terminals are on one of the two larger, flatsurfaces, of the housing. Typically, terminals occupy most of the areabetween the surface edges and any spacer or spacers. Note that in somecases, a spacer may be an encapsulated chip or a ground pad.

Each of the terminals may include a small, approximately sphericalsolder ball that firmly adheres to a lead from the internal circuitrypenetrating surface, hence the term “ball grid array.” Each terminal andspacer projects a small distance away from the surface, with theterminals projecting farther from the surface than the spacers. Duringassembly, all terminals are simultaneously melted, and adhere tosuitably located conductors previously formed on the circuit board.

The terminals themselves may be quite close to each other. Some havecenterline spacings of as little as 0.3 mm, and even relatively widelyspaced terminals may still be around 1.5 mm apart. Spacing betweenadjacent terminals is often referred to as “pitch.”

In addition to the factors mentioned above, BGA microcircuit testinginvolves additional factors.

First, in making the temporary contact with the ball terminals, thetester should not damage the S&P terminal surfaces that contact thecircuit board, since such damage may affect the reliability of thesolder joint for that terminal.

Second, the testing process is more accurate if the length of theconductors carrying the signals is kept short. An ideal test contactarrangement has short signal paths.

Third, solders commonly in use today for BGA terminals are mainly tinfor environmental purposes. Tin-based solder alloys are likely todevelop an oxide film on the outer surface that conducts poorly. Oldersolder alloys include substantial amounts of lead, which do not formoxide films. The test contacts must be able to penetrate the oxide filmpresent.

Fourth, the thickness of the device body and the ball are manufacturedto a large tolerance relative to the length of the contact signal path.To make temporary contact with ball terminals within the proper forcerange, the contacts traditionally require a large compliant range toaccommodate this tolerance. However, as the contact signal paths aremade shorter, it becomes very difficult to provide the large compliantrange while maintaining contact robustness for adequate product life dueto the reduced length of the contacts.

Fifth, during the production testing process a robotic arm presents thedevice to the contacts for electrical test. This robotic arm sometimesfails to remove a device from the contacts and attempts to present asecond device to the contacts for testing, thus applying a significantload to the socket. Also, in some cases the robotic arm unintentionallyinserts devices at incorrect orientations which can cause damage to thecontact tips.

BGA test contacts currently known and used in the art employ spring pinsmade up of multiple pieces including a spring, a body and top and bottomplungers. The many components and longer signal length are not optimalfor high frequency testing.

United States Patent Application Publication No. 2003/0192181, titled“Method Of Making An Electronic Contact” and published on Oct. 16, 2003,shows microelectronic contacts, such as flexible, tab-like, cantilevercontacts, which are provided with asperities disposed in a regularpattern. Each asperity has a sharp feature at its tip remote from thesurface of the contact. As mating microelectronic elements are engagedwith the contacts, a wiping action causes the sharp features of theasperities to scrape the mating element, so as to provide effectiveelectrical interconnection and, optionally, effective metallurgicalbonding between the contact and the mating element upon activation of abonding material.

According to United States Patent Application Publication No.2004/0201390, titled “Test Interconnect For Bumped SemiconductorComponents And Method Of Fabrication” and published on Oct. 14, 2004, aninterconnect for testing semiconductor components includes a substrate,and contacts on the substrate for making temporary electricalconnections with bumped contacts on the components. Each contactincludes a recess and a pattern of leads cantilevered over the recessconfigured to electrically engage a bumped contact. The leads areadapted to move in a z-direction within the recess to accommodatevariations in the height and planarity of the bumped contacts. Inaddition, the leads can include projections for penetrating the bumpedcontacts, a non-bonding outer layer for preventing bonding to the bumpedcontacts, and a curved shape which matches topography of the bumpedcontacts. The leads can be formed by forming a patterned metal layer onthe substrate, by attaching a polymer substrate with the leads thereonto the substrate, or by etching the substrate to form conductive beams.

According to U.S. Pat. No. 6,246,249 titled “Semiconductor InspectionApparatus And Inspection Method Using The Apparatus” and issued on Jun.12, 2001 to Fukasawa et. al., a semiconductor inspection apparatusperforms a test on a to-be-inspected device which has a sphericalconnection terminal. This apparatus includes a conductor layer formed ona supporting film. The conductor layer has a connection portion. Thespherical connection terminal is connected to the connection portion. Atleast a shape of the connection portion is changeable. The apparatusfurther includes a shock absorbing member, made of an elasticallydeformable and insulating material, for at least supporting theconnection portion. A test contact element of the disclosure for makingtemporary electrical contact with a microcircuit terminal comprises atleast one resilient finger projecting from an insulating contactmembrane as a cantilevered beam. The finger has on a contact sidethereof, a conducting contact pad for contacting the microcircuitterminal.

In U.S. Pat. No. 5,812,378 titled “Microelectronic Connector ForEngaging Bump Leads” and issued on Sep. 22, 1998 to Fjelstad et. al., aconnector for microelectronic includes a sheet-like body having aplurality of holes, desirably arranged in a regular grid pattern. Eachhole is provided with a resilient laminar contact such as a ring of asheet metal having a plurality of projections extending inwardly overthe hole of a first major surface of the body. Terminals on a secondsurface of the connector body are electrically connected to thecontacts. The connector can be attached to a substrate such amulti-layer circuit panel so that the terminals on the connector areelectrically connected to the leads within the substrate.Microelectronic elements having bump leads thereon may be engaged withthe connector and hence connected to the substrate, by advancing thebump leads into the holes of the connector to engage the bump leads withthe contacts. The assembly can be tested, and if found acceptable, thebump leads can be permanently bonded to the contacts.

According to United States Patent Application Publication No.2001/0011907 titled “Test Interconnect For Bumped SemiconductorComponents And Method Of Fabrication” and published on Aug. 9, 2001, aninterconnect for testing semiconductor components includes a substrate,and contacts on the substrate for making temporary electricalconnections with bumped contacts on the components. Each contactincludes a recess and a support member over the recess configured toelectrically engage a bumped contact. The support member is suspendedover the recess on spiral leads formed on a surface of the substrate.The spiral leads allow the support member to move in a z-directionwithin the recess to accommodate variations in the height and planarityof the bumped contacts. In addition, the spiral leads twist the supportmember relative to the bumped contact to facilitate penetration of oxidelayers thereon. The spiral leads can be formed by attaching a polymersubstrate with the leads thereon to the substrate, or by forming apatterned metal layer on the substrate. In an alternate embodimentcontact, the support member is suspended over the surface of thesubstrate on raised spring segment leads.

U.S. Pat. Nos. 9,007,082 and 9, 261,537 are hereby incorporated byreference for background material to avoid the need to restate concepts.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 a sectional perspective view of a plurality of pins (upper 20,lower 30) contacting a DUT ball 2, with an interposer 50.

FIG. 2 illustrates a plan sectional view of FIG. 1.

FIG. 3 illustrates a plan sectional view of FIG. 2 rotated 90 degrees(side view).

FIG. 4 illustrates a perspective view like FIG. 1 taken from above.

FIG. 5 illustrates is a top perspective view of plate 260 showing onlychamfered/countersunk-bored recesses apertures 252.

FIG. 6 illustrates a view like FIG. 1.

FIG. 7 illustrates a view like FIG. 2.

FIG. 8 illustrates a view like FIG. 3.

FIG. 9 illustrates a view like FIG. 4.

FIG. 10 illustrates a view like FIG. 5 except that one aperture is acounterbored/sunk type 254.

FIG. 11 illustrates a view like FIG. 1.

FIG. 12 illustrates a view like FIG. 5 except that a metallic trace 302provides a ground plane for several apertures and surrounds otherapertures.

FIG. 13 illustrates a pin pair 20/30 where the upper pin 20 includes atransverse section 310 of cross bar flanges 312/314. The edges of theseflanges are diagonally formed or slanted.

FIG. 14 illustrates a pin pair like FIG. 13 except that cross barflanges are replaced by a bulbous portion 316.

FIG. 15 illustrates a perspective view of a pin array with top layers260, 270 and 280 removed showing the elastomeric layer/matrix 290.

FIG. 16 illustrates a view like FIG. 15 except the downstop/antiintrusion layer is formed of individual disks 330 which sit atop theelastomer 290.

FIG. 17 illustrates a sectional view of the subject matter of FIG. 1with the device under test (DUT) removed.

FIG. 18 illustrates a view like FIG. 15 except that layer 280 has notbeen removed.

FIG. 19 illustrates a perspective view of an alternative embodiment toFIG. 15.

FIG. 20 illustrates a side plan view of FIG. 19.

FIG. 21 illustrates a perspective view of an alternative embodiment toFIG. 16.

FIG. 22 illustrates a close up view of a portion of FIG. 21.

FIG. 23 illustrates a view like FIG. 18 except including electricaltraces 440 which provide, for example grounding connections to thedownstop plate 290.

FIG. 24 illustrates a top view of FIG. 23.

FIG. 25 illustrates a bottom perspective view of an alternate embodimentof a pin pair.

FIG. 26 illustrates a tongue and grove version of FIG. 25.

FIG. 27 illustrates side perspective view of FIGS. 25 and 26.

FIG. 28 illustrates a side perspective view of FIG. 25.

FIG. 29 illustrates another side perspective view of FIG. 25.

FIG. 30 illustrates a perspective view of pin 29 of FIG. 25.

FIG. 31 illustrates a perspective view of pin 29 with a tongue andgroove style recess 454.

FIG. 32 illustrates a perspective view of pin 20 which mates with pin 30of FIG. 31.

FIG. 33 illustrates an end perspective view of FIG. 32.

FIG. 34 illustrates an alternative embodiment where the elastomer matrix290 is replaced by a plurality of spherical elastomeric balls 390.

FIG. 35 illustrates an alternative embodiment where the elastomer matrix290 is replaced by a plurality of elastomeric sheets 490.

FIG. 36 illustrates an alternative embodiment where the elastomer matrix290 is replaced by plurality springs 590.

FIG. 37 illustrates a close up perspective view of FIG. 36 showing thesprings.

FIG. 38 illustrates a view like FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

To the extent that a reference numeral is not defined herein, referenceshould be had to U.S. Pat. No. 9,261,537 which may have the samereference numeral and the component labels as in '537, though not thesame description. When a robotic hander inserts a BGA IC into a testsocket, there is always the possibility of causing damage to the(solder) balls on the array due to misalignment or over-force. This willeither destroy/damage the IC, damage the test socket or result in aunreliable test, or all of the above. By creating a receiver which canaccommodate all or part of the ball contact but limit its penetrationinto the test socket and test pins, these adverse occurrences areminimized.

This disclosure is a test socket assembly used with a BGA or eWLB(together referred to as BGA) type package device under test (DUT) and aprinted circuit board (PCB). The test socket makes temporary electricalcontact between the DUT and the PCB. It is unique because the previouslyvulnerable cartridge, which holds the pin pairs and elastomer, is nowprotected by a floating ball guide for package test. In addition toprotecting the cartridge, the floating ball guide provides a hardstopfor the DUT that limits the travel of the DUT ball and/or DUT body whichmakes the contact overdrive repeatable.

This test socket includes any or all of the following:

a) a housing aligns the contactor to the PCB. It is a generally rigidstructure with mounting and alignment features near the corners and apassage near the center where the cartridge is received.

b) a cartridge includes:

-   -   i) PCB side contact;        -   (1) an alternate contact with interlocking structure            improves high frequency signal integrity by ensuring that            the wedge to wedge interface is mated and motion is            coplanar.    -   ii) DUT side probe;        -   (1) the preferred geometry is conductive wedge-cross            bar-stem-sharp tip.        -   (2) an alternate geometry is more uniform section to            minimize impedance mismatch.        -   (3) an alternate is insulated coating on contact to control            signal loss to the guide plate and neighbor probes.        -   (4) an alternate tip geometry is multi finger/times which            provides wipe action on DUT ball rather than penetration.    -   iii) elastomeric member;        -   (1) an elastomeric/silicone slab with a pattern of recesses            that bias the probes on the DUT balls.        -   (2) the elastomeric member can be made with spheres            embedded.        -   (3) the elastomer can be modified on DUT and/or PCB side to            achieve anti-intrusion by the pin body.        -   (4) the elastomeric member can be made with wires embedded.        -   (5) coil springs may be used for the elastomer or individual            O-rings around the pin pairs    -   iv) using retaining layers align the contacts to each other and        prevent intrusion of the probe to the elastomer.        -   (1) use of polyester or polyimide film with a pattern of            through features to accept the DUT side probe.        -   (2) an alternate method of preventing intrusion of the probe            to the elastomer is to use independent film donuts /rings            for each probe instead of one continuous anti-intrusion            layer.        -   (3) a retainer /anti-intrusion layer may be made of            polyimide or equivalent with metallic layer sandwiched            between non-conductive layers. This provides a second            electrical path to the probe that can be used for redundant            paths, high precision analog measurements, or additional            current carrying capability.    -   c) the floating guide plate provides lateral alignment of the        DUT to the cartridge and limits the vertical travel of the DUT.        -   i) in the preferred embodiment, the guide plate is made of            insulative plastic or ceramic structure with a wide opening            for the DUT giving way to sloped faces for coarse alignment.            There is a pocket at the bottom with a pattern of            countersink, counter bore, or other alignment features for            each DUT ball. Blind holes are located at the corners for            return springs or other biasing structures (like an            elastomer) to provide the “floating” effect.        -   ii) an alternate embodiment has unique c-sink or counter            bores at high frequency signal locations for air gap. An            alternate embodiment has insulative plastic or ceramic            structure with metallization on surface in a pattern that            shields signals and connects to ground locations        -   iii) another variation is as above but the material is            conductive metal and a coating is selectively applied to            maintain electrical isolation.        -   iv) ball guide limits vertical travel to protect and            optimize the performance of the cartridge. This improvement            accurately controls the vertical travel yielding consistent            performance over the life of the contactor.    -   d) the plate may have metal structure with insulative inserts at        signal locations.

FIG. 1 illustrates a perspective view of a plurality of pins (upper 20,lower 30) contacting a DUT ball 2, with an interposer 50. The interposerhas a plurality of recesses 250 sized to receive balls 2 (in the case ofa ball grid array—BGA IC), some recesses being oversized 254 andalternatively, some being beveled 252 to provide a ball stop. Therecesses can be cylindrical or have a beveled recess or an arcuaterecess in place of the bevel shown. Arcuate can be a partial sphericalshape generally approximating the ball on a BGA. These shapes createball stop limiters to prevent the ball from damaging the pin which isengaged.

The apertures/recesses in the ball guide are preferably sized to receiveat least part a ball contact but small enough to prevent the entire ballcontact from passing therethrough. The depth of the recesses is lessthan the height of the ball contacts off the DUT, so that only part ofthe ball contact may engage the ball guide.

The ball stop limits DUT ball z-direction (up-down into the test socket)travel, and causes pin 20 to be deflected/compressed to a morerepeatable height than it would be if the device z-direction travel wascontrolled simply by the robotic chip inserter's arm overdrive/sensorsetting. Controlling the z-direction travel with the ball stop improvesrepeatability by removing the relatively large tolerances of the DUTbody thickness and ball protrusion from the overdrive tolerance stack.Instead the balls are pushed into the ball stop until the robotic armsenses a critical force threshold is met.

This ball guide 260 may sit atop an elastomeric layer 290 which providesresilience to the ball guide. A robotic arm chip inserter may not insertwith just the right force. Some of the shock can be absorbed in theresilient layer, but the balls themselves are also constrained by thecounter-bores which prevent the balls from driving the pins too deeplyinto their package.

The apertures/counter-bores are sized to receive at least part a ballcontact but small enough to prevent the entire ball contact from passingtherethrough.

By setting that force threshold higher than the force required to fullycompress the floating ball guide, the device ball will be repeatedlycompressed to the same height above the load board.

Interposer includes several parts. The top layer 260, which may be afloating ball guide, includes a plurality of recesses 252 or 254 sizedto permit pins 20 to extend therethrough and to allow balls 2 to beseated in the plurality of recesses 252/254 which may be doublecounter-bored with recess 255. The floating ball guide may engage theDUT with a force opposite the direction of the robotics arm travel priorto the DUT ball touching the electrical contacts. This preliminaryengagement with the floating ball guide protects the contact pins fromthe initial impact of the device and extends the contact life. Anup-stop layer 270, below 260, may be provided to prevent the pin 20 fromtraveling into layer 260 in response to compressive forces on the pinpair tending to drive the upper pin upwardly. A downstop layer 280prevents the pin from directly engaging the elastomeric layer 290.

Elastomeric layer 290 may be a solid portion except in the area of thepins where it is preferably a honeycomb which has apertures for pins20/30 but also provides the force which keeps these pins in slidableengagement with each other. The honeycomb pattern includes expansionspaces to allow pin pairs to expand laterally as they slide by eachother.

FIG. 2 illustrates a plan sectional view of FIG. 1.

FIG. 3 illustrates a plan sectional view of FIG. 2 rotated 90 degrees(side view).

FIG. 4 illustrates a perspective view like FIG. 1 taken from above.

FIG. 5 illustrates is a top perspective view of plate 260 showing onlychamfered/counter-sunk-bored recesses apertures 252. In this embodimenta metal trace 302 surrounds the aperture 252. Metalizing parts of theplate can be advantageous for impedance matching and crosstalkisolation.

FIG. 6 illustrates a view like FIG. 1.

FIG. 7 illustrates is a view like FIG. 2.

FIG. 8 illustrates FIG. 8 is a view like FIG. 3.

FIG. 9 illustrates is a view like FIG. 4.

FIG. 10 illustrates is a view like FIG. 5 except that one aperture is acounterbored type 254. In this embodiment several bores are bounded by ametalizing layer/trace 302 which may be grounded. Note that FIG. 10 mayalso be provided without a metal trace 302.

FIG. 11 illustrates a view like FIG. 1.

FIG. 12 illustrates a view like FIG. 5 except that a metallic trace 302provides a ground plane for several apertures and surrounds otherapertures.

FIG. 13 illustrates a pin pair 20/30 where the upper pin 20 includes atransverse section 310 of cross bar flanges 312/314. The edges of theseflanges are diagonally formed or slanted.

FIG. 14 illustrates a pin pair like FIG. 13 except that cross barflanges are replaced by a bulbous portion 316. Bulbous portion 316 islocated between the tip end and the sliding surface end of the upper pin(though the same bulbous structure can be applied to the lower pin). Thebulbous portion is an expanded part of the pin body between the ends andhas an arcuate shape on one or both of its sidewalls. The arcuate shapemay be mirror image or dissimilar in shape. From the bulbous portion tothe tip a sloping taper is preferable.

FIG. 15 illustrates a perspective view of a pin array with top layers260, 270 and 280 removed showing the elastomeric layer/matrix 290 whichis formed of a pattern of larger spaced and smaller apertures forreceiving pins 20. The open spaces allow for the deflection of theelastomer without substantially raising the load/bias force on the pinpairs as they slide by each other and deflect the elastomer.

FIG. 16 illustrates a view like FIG. 15 except the downstopanti-intrusion layer is formed of individual disks 330 which sit atopthe elastomer 290. The disks preferably have sufficient diameter toextend at least beyond a portion or all of the flanges 310. By havingseparate/singulated disks instead of a single anti-intrusion plate, eachpin is able to respond independently to deflection by the BGA.

FIG. 17 illustrates a sectional view of the subject matter of FIG. 1with the device under test (DUT) removed.

FIG. 18 illustrates a view like FIG. 15 except that layer 280 has notbeen removed.

FIG. 19 illustrates a perspective view of an alternative embodiment toFIG. 15 where the pin pairs 20/30 are maintained biased together by anelastomeric tubular ring 410 which preferably snuggly surrounds thelower portion 20 b of pin 20 and the lower upper portion 30 a if pin 30in slidable relationship. This ring/band 410 is preferably tubular butmay also be a flat band. It may replace elastomer 290 or be used on somepins while others use the elastomer 290. It may also be used tosupplement elastomer 290 for pins that require a higher bias force tomaintain an adequate low impedance connection. The ring or band is anelastomeric material which engaged the lower distal part 20 b of theupper pin and any part of the lower pin and binds them together but in aslideably relationship. The ring may also be a band which is flat ornon-tubular.

FIG. 20 illustrates a side plan view of FIG. 19.

FIG. 21 illustrates a perspective view of an alternative embodiment toFIG. 16 where the upper portion pin 20a is formed of a cylindrical“basket” section 412 and a plurality of vertical tines 418, eachterminating at its distal end in a outwardly splayed/deflected portion422 thereby forming a basket 430 for ball 2 (shown in in FIG. 1) of theDUT. The tines may be lateral deflectable on to absorb impact forces ofthe DUT ball when placed in the test socket by a robotic handler. It canalso compensate misalignment of the balls 2 on the DUT due domanufacturing tolerances. The tines are joined at a base 202 by aconcentric ring 412

FIG. 22 illustrates a close up view of a portion of FIG. 21.

FIG. 23 illustrates a view like FIG. 18 except including electricaltraces 440 which provide, for example grounding connections to thedownstop plate 290. Some apertures may need ground isolation and thuswill be plated around (see FIG. 12). This figure illustrates how aplurality of traces can connect plating 302 to a common ground.

FIG. 24 illustrates a top view of FIG. 23.

FIG. 25 illustrates a bottom perspective view of an alternate embodimentof a pin pair which has a sliding interlocking joint, which includes anengagement notch 450, where one pin includes a land 452 and the otherpin includes a recess 454 sized to receive the land. The land and therecess can be on either pin other than shown in the figure. Thisembodiment uses pin pairs 20/30 as in prior embodiments but provides anadditional or alternate way of insuring constant electrical contactbetween the pairs yet provide for a slidable relationship therebetween.

FIG. 26 illustrates a tongue and groove version of FIG. 25 where theland includes side extensions spaced from its base and the recess islike sized to allow sliding but the pins cannot accidentally separate. Adovetail cut or other captured relationship is possible, such as a balland socket, etc. In short, the pins maintained in contact at all timesand the surface area of contact is substantially increased by theinterlocking structure. This also insures alignment between the twopins. The tongue/groove or other interlocking structure can be reversedfrom what is shown so that either pin may have the projection and theother have the grove. FIG. 26 shows an elevated tongue 452 and arecessed groove 454 with the tongue partially encapsulated within thegroove.

FIG. 27 illustrates a side perspective view of FIGS. 25 and 26 with aV-shaped groove.

FIG. 28 illustrates a side perspective view of FIG. 25.

FIG. 29 illustrates another side perspective view of FIG. 25.

FIG. 30 illustrates a perspective view of pin 29 of FIG. 25.

FIG. 31 illustrates a perspective view of pin 29 with a tongue andgroove style recess 454.

FIG. 32 illustrates a perspective view of pin 20 which mates with pin 30of FIG. 31.

FIG. 33 illustrates an end perspective view of FIG. 32.

FIG. 34 illustrates an alternative embodiment where the elastomer matrix290 is replaced by a plurality of spherical elastomeric balls 390 andthe pin pairs are surrounded by the balls, either in cavities orcompletely filling the space between pin pairs, to provide the biasforce to maintain the pins in slidable contact. The balls are smallspheres which are compressible which fill the available spaced so thatthe pin pairs are maintained in contact. The balls can also beconductive or non-conductive. It would be preferable to make the wallsconfining the spheres rigid or semi-rigid to apply sufficient force intothe spheres.

FIG. 35 illustrates an alternative embodiment where the elastomer matrix290 is replaced by a plurality of elastomeric planar sheets 490 stackedon each other, such as vertically or horizontally and the pin pairs aresurrounded by the sheets, either in cavities or completely filling thespace between pin pairs, to provide the bias force to maintain the pinsin slidable contact.

FIG. 36 illustrates an alternative embodiment where the elastomer matrix290 is replaced by a plurality springs 590 which engage the pin pairs toprovide the bias force to maintain the pins in slidable contact but alsoprovide an upward bias force on pins 20. The inner diameter of thesprings is small enough to maintain the pins in a slidable mated statedto each other. The spring can have multiple diameters to fit the varyingcross section of the pin pairs with the top and bottom portions beingsmall diameter and the middle being largest. The two springs for eachpin pair can be used, one for the top and bottom and the middle nothaving a spring.

FIG. 37 illustrates a close up perspective view of FIG. 36 showing thesprings engage a shoulder of cross member 312/314 to maintain biasforce.

FIG. 38 illustrates a view like FIG. 4.

The description of the invention and its applications as set forthherein is illustrative and is not intended to limit the scope of theinvention. Variations and modifications of the embodiments disclosedherein are possible and practical alternatives to and equivalents of thevarious elements of the embodiments would be understood to those ofordinary skill in the art upon study of this patent document. These andother variations and modifications of the embodiments disclosed hereinmay be made without departing from the scope and spirit of theinvention.

1. A test socket for testing integrated circuit devices under test (DUT)having ball contact comprising: a. a housing; b. longitudinallycompressible unit, within the housing, which forms a plurality oftemporary mechanical and electrical connections for use between a deviceunder test having a plurality of terminals and a load board having aplurality of contact pads, each contact pad being laterally arranged tocorrespond to said terminals; c. protective ball guide having a topsurface, a plurality of apertures for contact pins, said apertures insaid top surface, at least one of said apertures including recessessized to receive at least part a ball contact but small enough toprevent the entire ball contact from passing therethrough; said recessesincluding a concave portion having arcuate sidewalls; d. an elastomericbias element resiliently supporting said ball guide; e. a longitudinallyresilient, electrically insulating interposer between the top and bottomcontact plates; said interposer including a resilient grid matrix ofinterconnected cells formed of an elastomeric material, each cellincluding longitudinal holes therethrough; f. a plurality oflongitudinally compressible, electrically conductive pin pairs extendingthrough longitudinal holes in the top contact plate, the interposer andthe bottom contact plate, each pin pair in the plurality being laterallyarranged to correspond to said terminal on the device under test; g. aplurality of longitudinally compressible, electrically conductive pinpairs extending through longitudinal holes in the top contact plate, theinterposer and the bottom contact plate, each pin pair in the pluralitybeing laterally arranged to correspond to said terminal on the deviceunder test; wherein when a particular pin pair is longitudinallycompressed, the pins in the pair slide past each other, an interfacesurface that is inclined with respect to a surface normal of theinterposer.
 2. The tester of claim 1 wherein the interposer cells aresized to receive said pin pairs and wherein upper pin includes atransverse section of greater cross section than other parts of theupper pin, and wherein said tester further includes separateanti-intrusion disks interposed between at least some of said pinsbetween their transverse section and said elastomeric bias element, sothat deflection of the upper pin is prevented from penetrating said biaselement by said disk and wherein each disk is independently engagable.3. The tester of claim 1 wherein said bias element is a resilient ringwhich binds the pin pairs together.
 4. The tester of claim 1 whereinbias element is a plurality of resilient compressible balls surroundingthe pin pairs.
 5. The tester of claim 1 wherein the ball guide forms ahard stop for the DUT ball, thereby limiting deflection of the pinpairs.
 6. The tester of claim 1 wherein the ball guide includes a firstchamfered rim sized to receive and restrain further entry of the ball.7. The tester of claim 1 wherein said pin pairs include an upper andlower pin and wherein said pin pairs including a sliding interlockingjoint between the two to prevent separation and to maintain slidingelectrical contact.
 8. The tester of claim 7, wherein said slidinginterlocking joint includes a land on the pin and a recess on the otherpin, the land and recess sized to be in slidable and electricalengagement.
 9. The test of claim 8 wherein said land and recess is atongue and groove.
 10. A test socket for testing integrated circuitdevices under test (DUT) having ball contact comprising: a. a housingfor receiving a DUT; b. longitudinally compressible unit, within thehousing, which forms a plurality of temporary mechanical and electricalconnections for use between a device under test having a plurality ofterminals and a load board having a plurality of contact pads; c.protective ball guide having a top surface, a plurality of apertures forpins pairs, said apertures, said apertures in said top surface, at leastone of said apertures including recesses sized to receive at least parta ball contact but small enough to prevent the entire ball contact frompassing therethrough; said recesses including a concave portion havingarcuate sidewalls; said pin pairs including an upper and lower pin inslidable electrical contact, said upper pin including a transversesection having a greater cross section than other parts of the upperpin, and wherein said tester further includes singulated anti-intrusiondisks interposed between at least some of said upper pins between theirtransverse section and said compressible unit, so that deflection of anupper pin having said disk is prevented from penetrating saidcompressible unit by said disk and with one disk deflection beingindependent of any other disk deflection.
 11. The tester of claim 10wherein the top surface of the ball guide includes metalized coatingsurrounding at least some of the apertures.
 12. The tester of claim 11wherein said ball guide includes electrical traces connected to saidmetalized coating.
 13. The tester of claim 10 wherein said ball guide isresiliently deflectable.
 14. The tester of claim 13 wherein said ballguide is supported by resilient springs.
 15. A method of protecting testpins in a test socket from being overdriven by insertion of a deviceunder test (DUT) having ball contacts of predetermined height, a testsocket for testing integrated circuit devices under test (DUT) havingball contact; the test socket having a housing and protective ball guidehaving a top surface, comprising the steps of: a. forming a plurality ofapertures in said ball guide, said apertures being sized to receive testpins; b. counter-boring said apertures, adjacent said top surface toinclude an arcuate recess, said recesses having a depth less than thedepth of height of a ball contact; so that the balls are prevented fromover-driving said test point by engaging said recesses.
 16. The methodof claim 15 including forming the recess with a beveled edge adjacentthe top surface.